The present invention relates to a closeable opening device for a container made of plastic film, said device consisting of a base, which comprises a cylindrical spout and a flange for mounting on the container, a screw cap that is screwably connected to the base, as well as a cylindrical cutting element having outer thread, wherein the cutting element is open on both sides in the axial direction and engages an inner thread in the spout of the base, wherein at least one driving dog is present in the screw cap, which displaces the cutting element that has at least one driving dog arranged therein downwards in a screw-like manner upon initial opening of said screw cap, and wherein the cutting element has at least one cutting tooth on the lower edge.
Closeable opening devices of the type mentioned above have been known for a long time for containers made of laminated film material. More and more containers have recently come on the market, which are manufactured from pure, single- or multi-layered plastic films. Such containers are referred to as tubular bags or for the most part the English term “pouches” is used. The closeable opening devices typically comprise a base attached directly to the container or respectively the tubular bag and a screw cap detachably attached to the base for closing a spout in said base. In order to mount the opening device, a flange of the base is non-detachably attached to the plastic film of the tubular bag in a cohesive connection by means of ultrasonic welding.
Opening devices of the type mentioned here have been known for many years. By way of example, reference is made in this regard to the patent documents U.S. Pat. No. 5,147,070 A, U.S. Pat. No. 5,141,133 or also to the WIPO patent publication 2004/000667 and the WIPO patent publication 2004/03055.
Opening devices of this type are manufactured in great quantities and mounted on containers. In the beginning, it was hereby assumed that the same opening devices, as they were mounted on containers made from laminated cardboard combined with plastic films, could be used on containers that were made from pure plastic films. This is in fact correct in its basic concept; however, the mounting of the opening devices on pure plastic films is only possible by means of ultrasonic welding and correspondingly measures were taken in this regard which improve the welded connection and perform the same more quickly.
In order to improve the weld, attention has been placed up until now on the configuration of the energy-introducing ribs. The patent documents JP 200016453 and also JP 2000344264 disclose, for example, solutions in this regard.
In addition, the thickness of the flange on the base has been embodied ever thinner to save energy on the one hand and to reduce the cycle times of the welding process on the other hand. Because this lies in the area of the expert's decision making and this is also a part of the know-how of the manufacturer, there is no suggestive information in this regard in the patent literature.
The entire closeable opening device is more flexible due to of the thin-walled design of the flange. As a result, the danger exists that the cutting element can inadvertently displace relative to the spout prior to initial use as well as after initial use. In particular after the initial opening, the problem arises on account of this relative displacement that the cutting element possibly deforms toward the top or bottom in the cylindrical spout due to the deformation of said spout or due to the flange welded on the container such that the cutting element moves either upward or downward in the cylindrical spout. If said cutting element moves upward, the driving dogs on the screw cap come again in contact with the corresponding driving dogs in said cutting element in an undesirable manner and said cutting element also in turn moves upward or downward when the closure is repeatedly opened or closed. This is undesirable because it can occur as a result of said repeated movements that the partially cut-open film, which practically protrudes downward into the container in the form of a flap, becomes completely separated and falls into the container. Because these containers are frequently used for food items, such as drinks or sauces, aggravating liability problems can thereby arise. It is likewise undesirable if the cutting element moves somewhat further downward and then is no longer held in the spout and consequently falls into the container. In so doing, there is hardly a threat posed to the health of the user, but the cutting element can come to rest in front of the spout during further use and impair the function thereof to such an extent that the pouring stream is deflected, which can correspondingly lead to clothes becoming soiled.